linux-kernel - Re: rhashtable: Prevent spurious EBUSY errors on insertion

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Message-ID: <20151217084809.GC9239@gondor.apana.org.au>
Date:	Thu, 17 Dec 2015 16:48:09 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Xin Long <lucien.xin@...il.com>
Cc:	Phil Sutter <phil@....cc>, davem <davem@...emloft.net>,
	network dev <netdev@...r.kernel.org>,
	linux-kernel@...r.kernel.org, tgraf@...g.ch,
	fengguang.wu@...el.com, wfg@...ux.intel.com, lkp@...org
Subject: Re: rhashtable: Prevent spurious EBUSY errors on insertion

On Thu, Dec 17, 2015 at 04:46:00PM +0800, Xin Long wrote:
>
> sorry for late test, but unfortunately, my case with rhashtalbe still
> return EBUSY.
> I added some debug code in rhashtable_insert_rehash(), and found:
> *future_tbl is null*
> 
> fail:
>         /* Do not fail the insert if someone else did a rehash. */
>         if (likely(rcu_dereference_raw(tbl->future_tbl))) {
>                 printk("future_tbl is there\n");
>                 return 0;
>         } else {
>                 printk("future_tbl is null\n");
>         }
> 
> any idea why ?

That's presumably because you got a genuine double rehash.

Until you post your code we can't really help you.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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